Holmes, 25, faces 166 criminal counts in connection with the July 20 attack on a movie theater in Aurora. Colo. Twelve people were killed and at least 70 injured in the July 20 shooting during a screening of “The Dark Knight Rises.” His preliminary hearing began Monday.

Aurora Police Det. Matthew Inqui, of the major crimes unit, said he interviewed witnesses who were inside Theater 9. They described a man in dark clothes standing near the emergency exit. They saw flashes of light and gunfire and said the gunman was calm as he moved along the aisles.

Inqui introduced the theater’s surveillance video, which shows Holmes, dressed in dark pants, a white shirt and a skull cap, scanning his ticket, handing it to a ticket agent and then walking to Theater 9. The video also shows the aftermath as dozens of terrified movie patrons fled the theaters.

Inqui testified Monday afternoon at the preliminary hearing, which is expected to run all week. The purpose of the hearing is to decide whether the prosecution has enough of a case for a trial.